The cosine rule

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Hi,

 

Wondering if anyone could tell me how the cosine rule can be the way it is - how it works the way/like it does... Or give me a link to a good explaination for the nature of the rule..

 

Cheers

[ajb]

Wikipedia.

Mathworld .

PlanetMath. (also see here)

 

and I an sure we can find many other websites. The above links provide proofs of the law.

 

If you have a specific question then please ask.